CI: Introduce auto for publishing packages

[jackw]

What this PR does / why we need it:
This PR introduces Auto as a solution for independently versioning and publishing the packages within this monorepo.

• Introduce Auto and configure
• Introduce Lerna (a necessary dependency of Auto) and configure
• Add Auto plugins to appreciate contributors and configure
• Reset version of sign-plugin for initial release
• Delete previous bump version and release workflows in favour of a release work using auto
• Update contributing docs related to versioning

Which issue(s) this PR fixes:

Fixes #118

Special notes for your reviewer:
As this PR has the release label attached when merged this PR should push new patch versions for both create-plugin and sign-plugin.

📦 Published PR as canary version: Canary Versions

✨ Test out this PR locally via:

npm install @grafana/create-plugin@0.4.1-canary.127.0910e06.0
npm install @grafana/sign-plugin@0.0.1-canary.127.0910e06.0
# or 
yarn add @grafana/create-plugin@0.4.1-canary.127.0910e06.0
yarn add @grafana/sign-plugin@0.0.1-canary.127.0910e06.0

[tolzhabayev]

Some questions

[tolzhabayev]

SEND IT!

[mckn]

LGTM! Added one small nit and one question.

[grafanabot]

🚀 PR was released in @grafana/create-plugin@0.4.1, @grafana/sign-plugin@0.0.1 🚀